Medical testing devices that use chemical reactions as a main analytical mechanism are being developed. In existing specimen tests, reagents are required for chemical analyses, preparation of reagents, chemical syntheses, and reaction detection on the order of milliliters (ml) to microliters (μl). Such tests performed using test-tubes or the like can now be performed on the order of nanoliters (nl) by formation of a fine reaction field using a litho-process technology and a thick film process technology. The micro total analysis system (μ-TAS) is a technology that utilizes such fine reaction fields. The μ-TAS technology is applicable to fields of genetic testing, chromosomal testing, cell testing and the like used for medical tests and diagnoses, biotechnologies, tests of substances present in very small amounts in the environment, research on the cultivating environment for agricultural products, genetic tests of agricultural products, and so forth. Existing tests are mainly performed by laboratory technicians who have skills for handling reagents. However, the test processes are complex, and a certain skill levels are required to operate the equipment. The μ-TAS technology has been attracting attention as a method having great advantages. The advantages include automatization, increased speed, increased accuracy, cost reduction, promptness, decreased negative effects on the environment, and so forth.
When such an advanced medical test system is generally used, it is necessary that a small amount of a reagent be introduced into a medical testing device used for the medical test system.
In the above-described medical testing devices and other devices having a fine structure, a fine flow passage is arranged to handle a reagent in the structure. However, the order of the amount of the reagent is different from that used in the existing tests. For this reason, it is very difficult to introduce a reagent into such a flow passage.
As PTL 1 discloses, a fluid device having a flat plate structure has an introducing space having a supply port open toward the vertical direction and a fine flow passage extending in a planar direction. The flat shape is utilized to form the flow passage while a direction of the opening and a direction in which the flow passage extends are different by 90 degrees in order to facilitate introduction of a liquid using a pipet or the like and holding of the introduced liquid. In order to receive a liquid from a liquid supply unit such as a pipet and hold the liquid, the introducing space needs to have a size larger than the size of the flow passage. Accordingly, sectional areas on one side and the other of a connecting portion, in which an end portion of the flow passage and the introducing space are connected, are significantly different from each other.
In this portion, air bubbles are easily formed in particular when the liquid is added or replaced, thereby causing various problems in the flow passage device.
In particular, small air bubbles tend to be formed when liquids are mixed. Accordingly, there is a high possibility of introduction of bubbles, that is, a phenomenon in which the bubbles formed are introduced into the flow passage along with the liquid.
In some cases, when a liquid flows in the flow passage along with bubbles in the flow passage of, for example, a heating system, the bubbles may expand and clog the flow passage. In addition, because of the difference in elasticity between fluid and gas, an intended transportation of the liquid is not achieved when a pressure is applied.
The above-described problems are significant problems when a reagent is added or replaced. In particular, in order to cause a reaction in a fine flow passage, a complex operation such as mixing or separating reagents is required. In order to do this, different reagents need to be sequentially introduced into the flow passage. At this time, when a preceding reagent remains in the introducing space, a following reagent is mixed with the preceding reagent. This causes contamination of the reagent. In order to suppress effects caused by the contamination, the remaining amount of a preceding reagent may be decreased and a sufficient amount of a following reagent may be introduced. In this case, however, the above-described phenomenon in which bubbles are introduced is very likely to occur. Since the volume held by the flow passage is small and an interface formed in the connecting portion is easily moved, the interface formed in the connecting portion is easily moved toward the flow passage side by an application of a small amount of force.